Reynolds said plenty of people still file the old fashioned way, even though volume is down.

“We’ve seen a lot of diversion to electronic channels over the years. We know volume has decreased dramatically across the board,” Reynolds said, although he said the post office doesn’t have specific figures on how much mail filings have decreased with the prevalence of e-filing.

Contrary to what many may believe, Reynolds said that tax deadline day is not the busiest day of the year for the post office, even though facilities will see twice the traffic as a regular day.

“The busiest mailing day of the year is actually in mid-December during the holiday season,” Reynolds said.

Those filing their taxes on Monday might have had to shell out a few extra cents to mail their returns, as postal rates went up over the weekend. The price of additional postage, an extra ounce, went up from 17 cents to 20 cents.

“If you’re mailing a tax return that has more than five pages in it, you’ll probably have to add extra postage,” Reynolds said.

Postal Employees will be curbside, picking up last minute envelopes so you won’t have to get out of your car. There will even be a mobile stamp machine if you need extra postage.

“We’ve down-scaled the number of offices with extended hours or collectors on the street dramatically over the past several years,” Reynolds said. “Most Post Offices were never open until midnight on Tax Night anyway.”

Chicago’s main post office at 433 W. Van Buren St. is open until midnight on Monday.